I just replaced my ATI 9800 with a new GeForce 6800. OpenGL games seem to work pretty well, but I have a problem when exiting them. They hang when exiting, prior to switching the video mode back to the original desktop video mode. They also consume as much CPU as they can grab. When I strace the process, I simply see the following repeated over and over:

sched_yield() = 0

Since I'm often a lower res at this point, I end up having to kill the application and restart X to reset the resolution (ctrl alt +/- doesn't work here).

This seems to have started just after switching out my video card, and is happening consistently across several different games (including the ThinkTanks demo, UT2004, and Neverwinter Nights).